I have already elaborated on uninteresting and interesting labyrinths (see related posts, below). Unintersting labyrinths can be generated by simply attaching additional trivial circuits to the outside or inside of smaller labyrinths. Interesting labyrinths cannot be obtained this way. This particularly implies, that in interesting labyrinths the pathway may not enter the labyrinth on the outermost circuit or reach the center from the innermost circuit. The dual of an interesting labyrinth is another interesting labyrinth too.

This is different if we derive the complementary labyrinth of an interesting labyrinth. The resultung labyrinth may very well be an uninteresting labyrinth. Complementary labyrinths exist only for alternating labyrinths with an odd number of circuits. To obtain the complementary, the pattern of the original labyrinth is vertically mirrored without interrupting the connections between the outside or center of the labyrinth with their corresponding circuits. Labyrinths with an odd number of circuits always have a central circuit. When the pattern is mirrored, this circuit remains in position, whilst the other circuits change their positions symmetrically around it.

In a labyrinth with seven circuits, e.g., the central circuit is the one with number 4. After the mirroring, this remains in its position as number 4. The outermost circuit, number 1, transforms to the innermost circuit and obtains number 7, circuit 2 changes to circuit 6, circuit 3 to circuit 5, and vice versa.

Now, if in an interesting labyrinth the pathway first leads to the innermost circuit or reaches the center from the outermost circuit, then the complementary to this labyrinth will be an uninteresting labyrinth. This, because in the complementary, the path will enter the labyrinth on the outermost or reach the center from the innermost circuit. Thus, there exist pairs of complementary labyrinths, both of which are interesting and others in which one of the labyrinths is interesting and the other uninteresting.

Now I want to find out which are the pairs of interesting complementary labyrinths. The website of Tony Phillips provides best material for such a purpose. On one page, HERE, are included the seed patterns (left figures) and the patterns (right figures) of the interesting alternating labyrinths with up to 7 circuits. I therefore reproduce the page in fig. 2 and in the following add some comments to the items indicated with red letters:

- a) In addition to the circuits, Tony also counts the exterior (= 0) and the center (= one greater than the number of circuits) of a labyrinth. He refers to this as the depth of the labyrinth. A labyrinth with depth 4, thus, has three circuits, one with depth 6 has 5 circuits and so on.
- b) Below the two figures (seed pattern und pattern), in each case the sequence of circuits is listed. This also contains the zero for the exterior and the number for the center, here indicated with red boxes. The true sequence of circuits is the sequence of numbers between these boxes.
- c) If the labyrinth is self-dual, this is indicated as „s.d.“ after the sequence of circuits.
- d) If this is not the case, anyway only one of each dual example is shown in the figures. However, the sequence of circuits of the dual not shown is listed in parentheses below the sequence of circuits of the labyrinth shown.
- e) The patterns are drawn in such a manner that the course of the pathway leads from top right to bottom left. This is different from how I do it. I draw the pattern from top left to bottom right. As a consequence, the labyrinth that corresponds with the pattern by Tony rotates anti-clockwise, whereas in my case it rotates clockwise.
- f) Now, lets consider all interesting (including very interesting) labyrinths with 7 circuits. Of these, there are 22 (6 of them very interesting) interesting labyrinths. In fig. 2 the seed patterns and patterns of only 14 labyrinths are depicted. The missing 8, however, are duals, represented by the sequences of circuits in parentheses.

Among the interesting labyrinths with 7 circuits, only 2 exist, in which the pathway does not enter the labyrinth on the innermost circuit nor reach the center from the outermost circuit. And these two form the only pair of interesting labyrinths complementary to each other. We already know this pair from the first post of this series. It is the basic type labyrinth (g) and the labyrinth with the S-shaped course of the pathway (h).

These are self-dual and thus very interesting labyrinths. In the other 20 interesting labyrinths, the complementary in each case is an uninteresting labyrinth.

Thus, there are 42 different alternating labyrinths with one arm and 7 circuits. Among these, there are 8 pairs of interesting dual labyrinths, 6 self-dual very interesting labyrinths, but only 1 pair of interesting complementary labyrinths. In addition, there is no pair of interesting complementary labyrinths with less than 7 circuits.

Pairs of complementary interesting labyrinths seem to be relatively rare and thus something special.

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